Scott said after the round that it was dark and he had trouble
reading his putt on the second playoff hole. So called over
Williams for help (via
the LA Times):

"I don't get him to read too many putts. He said it's at
least two cups, it's going to break more than you think. I said,
'I'm good with that.' He was my eyes on that putt. It managed to
hang in. Amazing feeling."

Williams has been criticized for taking himself and his
duties as a caddie too seriously. But you have to give him credit
for stepping up and helping his boss sink the biggest putt of his
life.